Friday, 1 June 2018

Effect of Impurities in Water on Properties of Concrete

Common Impurities in Water  & their Permissible limits as per I.S Code:-

Name of Impurities                             Permissible limit

1.Organic matter                                     200 mg/lit
2.Inorganic matter                                   3000 mg/lit
3.Sulfates ( as SO)                                 400 mg/lit
4.Chlorides (as Cl)                                  
               a) For plain concrete                2000 mg/lit
               b)For R. C. C.                           500 mg/lit
5.Suspended matter                                2000 mg/lit

Effect of Impurities in Water on Properties of Concrete:-

                   The impurities in water used for preparation of concrete may affect the properties of concrete in the following way:

a)The strength & durability of concrete may be reduced due to the presence of impurities in the mixing water. Experiments shows that water containing excessive amount of dissolved salts reduces compressive strength by 10 to 30% of that obtained using potable water.

b)The setting time of cement may be changed. Presence of Zinc chlorides retards the setting of concrete to such an extent that no strength test are possible at 2 and 3 days .
On the other hands ,the presence of calcium chloride accelerates setting and hardening.

c)Presence of excessive chlorides cause dampness , surface efflorescence & increase the corrosion of reinforcing steel.

d)Presence of algae in water reduces the bond between aggregate & comet paste & thus lowering the strength of concrete.

e) Presence of sugar up to 0.15% by weight of cement retard the setting of cement and the early strength may be reduced.When the quantity of sugar is increase to 0.2% by weight of cement ,setting is accelerated.

f)Mineral oils not mixed with animal or vegetable oils have no adverse effect on the strength of concrete .But the presences of vegetable oils have detrimental effect on the strength of concrete,particularly at later ages.

MORE-Role of Water and Quality of Mixing Water in Concrete                                                                           

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